[ARM] 4650/1: AT91: New-style init of I2C, support for i2c-gpio

The AT91 I2C driver is currently marked as "broken" due to hardware
issues.  This patch enables AT91-based platforms to also use the
bitbanged GPIO for I2C.

This updates platform setup logic (setting up an i2c-gpio device
using the same pins as the i2c-at91 device, unless only the BROKEN
driver is enabled).

Also make use of the new-style initialization of I2C devices using
i2c_register_board_info().

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Andrew Victor <andrew@sanpeople.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 38 insertions, 3 deletions

diff --git a/arch/arm/mach-at91/at91rm9200_devices.c b/arch/arm/mach-at91/at91rm9200_devices.c
index 0417c165d50d..9296833f91cc 100644
--- a/arch/arm/mach-at91/at91rm9200_devices.c
+++ b/arch/arm/mach-at91/at91rm9200_devices.c
@@ -14,6 +14,7 @@
 #include <asm/mach/map.h>
 
 #include <linux/platform_device.h>
+#include <linux/i2c-gpio.h>
 
 #include <asm/arch/board.h>
 #include <asm/arch/gpio.h>
@@ -435,7 +436,40 @@ void __init at91_add_device_nand(struct at91_nand_data *data) {}
  *  TWI (i2c)
  * -------------------------------------------------------------------- */
 
-#if defined(CONFIG_I2C_AT91) || defined(CONFIG_I2C_AT91_MODULE)
+/*
+ * Prefer the GPIO code since the TWI controller isn't robust
+ * (gets overruns and underruns under load) and can only issue
+ * repeated STARTs in one scenario (the driver doesn't yet handle them).
+ */
+#if defined(CONFIG_I2C_GPIO) || defined(CONFIG_I2C_GPIO_MODULE)
+
+static struct i2c_gpio_platform_data pdata = {
+        .sda_pin                = AT91_PIN_PA25,
+        .sda_is_open_drain      = 1,
+        .scl_pin                = AT91_PIN_PA26,
+        .scl_is_open_drain      = 1,
+        .udelay                 = 2,            /* ~100 kHz */
+};
+
+static struct platform_device at91rm9200_twi_device = {
+        .name                   = "i2c-gpio",
+        .id                     = -1,
+        .dev.platform_data      = &pdata,
+};
+
+void __init at91_add_device_i2c(struct i2c_board_info *devices, int nr_devices)
+{
+        at91_set_GPIO_periph(AT91_PIN_PA25, 1);         /* TWD (SDA) */
+        at91_set_multi_drive(AT91_PIN_PA25, 1);
+
+        at91_set_GPIO_periph(AT91_PIN_PA26, 1);         /* TWCK (SCL) */
+        at91_set_multi_drive(AT91_PIN_PA26, 1);
+
+        i2c_register_board_info(0, devices, nr_devices);
+        platform_device_register(&at91rm9200_twi_device);
+}
+
+#elif defined(CONFIG_I2C_AT91) || defined(CONFIG_I2C_AT91_MODULE)
 
 static struct resource twi_resources[] = {
         [0] = {
@@ -457,7 +491,7 @@ static struct platform_device at91rm9200_twi_device = {
         .num_resources  = ARRAY_SIZE(twi_resources),
 };
 
-void __init at91_add_device_i2c(void)
+void __init at91_add_device_i2c(struct i2c_board_info *devices, int nr_devices)
 {
         /* pins used for TWI interface */
         at91_set_A_periph(AT91_PIN_PA25, 0);            /* TWD */
@@ -466,10 +500,11 @@ void __init at91_add_device_i2c(void)
         at91_set_A_periph(AT91_PIN_PA26, 0);            /* TWCK */
         at91_set_multi_drive(AT91_PIN_PA26, 1);
 
+        i2c_register_board_info(0, devices, nr_devices);
         platform_device_register(&at91rm9200_twi_device);
 }
 #else
-void __init at91_add_device_i2c(void) {}
+void __init at91_add_device_i2c(struct i2c_board_info *devices, int nr_devices) {}
 #endif